<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I would think that keeping them clean would provide that necessary friction </div></BLOCKQUOTE>
Definitely!! Clean & free of dirt, dust or whatever is what was behind the recommendation to wipe down the sides of the slide before retracting it, particularly if you have been parked with slides extended for an extended period. Clean helps, but slick does not.
So rubber cleaner would likely help, while "treatements" that leave the rubber shiny & slick definitely will not help. As with tires, I suspect the best "treatment" if any is needed would be to wash gently with mild soap and water, and rinse well. I would prefer plain water myself if I were doing it!
...I also learned that when I wash & wax the coach -- including the slide sides (mine are included in the full body paint) -- the wax on the wall can make the walls slick enough that the seals have trouble flipping! Clean is good! ...slick helps the dirt slide off, but doesn't help the seals flip! ...guess ya just gotta pick which you want ...waxed & slick slide sides, or seals that flip...